Definition
Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay
Phonolite is an uncommon extrusive igneous rock volcanic rock of intermediate chemical composition between felsic and mafic
History
Origin
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-
Discoverer
Unknown
Unknown
Etymology
From German Grauwacke, from grau grey + wacke
From the Greek meaning sounding stone because of the metallic sound it produces if an unfractured plate is hit
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
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Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock